Background

The International Headache Society (IHS) began developing a classification system for headaches in 1985. Now in its third edition (beta version), this system includes a tension-type headache (TTH) category, further defined as either episodic (frequent and infrequent) or chronic. Headache categories also are defined by whether they are associated with pericranial muscle disorders.
[1]

Episodic tension headache usually is associated with a stressful event. This headache type is of moderate intensity, self-limited, and usually responsive to nonprescription drugs.

Chronic tension headache often recurs daily and is associated with contracted muscles of the neck and scalp. This type of headache is bilateral and usually occipitofrontal.

TTH is the most common type of chronic recurring head pain. In the past, pain etiology was presumed to be the muscular contraction of pain-sensitive structures of the cranium, but the IHS intentionally abandoned the terms muscular contraction headache and tension headache because no research supports muscular contraction as the sole pain etiology.

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Pathophysiology

While both muscular and psychogenic factors are believed to be associated with tension-type headache, most are felt to be multifactorial. A study by Kiran et al indicated that patients with chronic tension headaches for longer then 5 years tended to have lower cortisol levels.
[2] This was postulated to be due to hippocampus atrophy resulting from chronic stress, a cause of chronic tension headaches. More recently it is believed that there is increased myofascial pain sensitivity caused by central factors such as sensitizatation of neurons in the supraspinal region as well as second order neurons in the spinal dorsal horn/trigeminal nucleus.
[3] Another mechanism of pain is decreased antinociception or inability of the body to stop painful stimuli to the supraspinal structures.
[4]

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Etiology

Stress may cause contraction of neck and scalp muscles, although no evidence confirms that the origin of pain is sustained muscle contraction.

Stress and/or anxiety

Poor posture

Depression

One study showed that patients with tension-type headache (TTH) have relatively weak neck extension muscles. According to results, these patients are 26% weaker than controls with respect to neck extension muscles, that they have a 12% smaller extension/flexion ratio, and that they have a borderline significant difference in the ability to generate muscle force over the shoulder joint.
[5, 6]

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Epidemiology

Statistics

Headaches account for 1-4% of all emergency department (ED) visits and are in the top most common reasons for a patient to consult a physician. Tension-type headaches (TTH) are common, with a lifetime prevalence in the general population ranging between 30% and 78% in different studies. They affect approximately 1.4 billion people or 20.8% of the population.
[7, 8] Of concern is that in 2010, opioids were administered in 35% of ED visits for headache compared to triptans, which were given in only 1.5% of visits.
[9]

TTH onset often occurs during the teenage years and affects three women to every two men. Previous studies in the United States had show that tension type headaches peaked in the fourth decade. However, European studies show that these headaches persist occurring even into the 6th decade of life.
[10]

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Prognosis

Tension-type headaches (TTH) may be painful, but are not harmful. Most cases are intermittent and do not interfere with work or normal life span. However, they may become chronic if life stressors are not changed.